This invention relates to superconducting ceramics having a high critical temperature.
The prior are has proposed the use of metals such as mercury and lead, intermetallics such as NbNd, Nb3Ge and Nb3Ga and ternary materials such as Nb3(Al0.8Ge0.2) as superconductors. Another type of superconducting material, superconductive barium-lead-bismuth oxides, is described in U.S. Pat. No. 3,932,315. However, only three-dimensional electron conduction takes place in such conventional superconducting materials, and the critical transition temperature (Tc) of such conventional superconducting materials cannot therefore exceed 25° K.
In recent years, superconducting ceramics have attracted widespread interest. A new material was first reported by researchers at the Zurich laboratory of IBM Corp. as Ba—La—Cu—O-type high temperature superconducting oxides. Also, La—Sr—Cu(II)—O-type superconducting oxides have been proposed. This type of superconducting material appears to form a quasi-molecular crystalline structure whose unit cell is constructed with one layer in which electrons have essentially one-dimensional motion. Such a superconducting material, however, has Tc lower than 30° K.